1) Stew the onion in butter over medium heat until soft, then zest the lemon and stir it with the onion.

2) Stir in the rice to coat all the grains of rice with butter.

3) Start adding broth 1/2 cup at a time. Adjust the heat so the broth just simmers. The broth will reduce and thicken into a sort of gravy. Every time that happens, add another half cup, then add the water. Stir frequently and continue until the rice is done. (If the broth and water are gone and the rice isn't done, keep adding more water.) Meanwhile, squeeze the lemon and add a couple tablespoons along with some broth. (Save the last bit of lemon juice to season the dish with at the end.)

4) When the rice is done—tender but not mushy—stir in the parmesan cheese. Season with salt, pepper, and the last bit of lemon juice. Serve with grated or shaved parmesan over the top.

Lemon Zest:
As you probably know, this is the outermost part—the yellow part—of the peel. If you have a zester, you can simple zest the lemon right into the pan. If you don't have this nifty tool, use a potato peeler to peel off the yellow part and mince it with a knife. (I'm not a fan of grating lemon zest because I always scrape my knuckles, but if you like that method, go for it.)